The present invention relates to semiconductor devices and more particularly to semiconductor integrated circuit devices including a step-down driver circuit for supplying a stepped-down potential to a driven circuit with a large load.
Generally, a driven circuit which uses an internal potential lower than an external power supply is configured to have power supplied from an internal step-down power supply circuit which generates a constant voltage based on a reference potential. The driven circuit is, when being active, supplied with an internal potential and is, when being inactive, kept reset to GND potential (reference potential). Generally, a PMOS transistor, which is a switch element, is provided between the internal step-down power supply circuit and the driven circuit to be supplied with power. Power supply to the driven circuit is controlled by controlling turning on/off of the switch element.
Driven circuits to use an internal potential include, for example, driven circuits with large-scale loads such as sense amplifier driver circuits. According to Japanese Unexamined Patent Application No. 2000-57773, to reduce power routing of a step-down power supply so as to reduce circuit area requirement, a sense amplifier driver circuit to drive a large-load sense amplifier power supply line is provided for each array. The sense amplifier driver circuit includes a PMOS transistor having a switching function and a step-down function and supplies a stepped-down potential generated by stepping down an external voltage supplied from an external power supply using the PMOS transistor to a sense amplifier power supply line. In concrete terms, the stepped-down potential is generated by having the gate potential of the PMOS transistor controlled by a step-down circuit (differential amplifier circuit).